This invention relates to gelling agents and a method for preparing gels.
Calcium chloride or the like is usually used as a gelling agent to prepare gel compositions such as an alginate gel or others. However, when calcium chloride or the like is used as a gelling agent, it is necessary to remove the gelling agent by washing after the gel is prepared, which raises a problem of the loss of active ingredients in the gel by the washing process. Accordingly, more efficient gelling methods that do not require the washing for the removal of the gelling agent have been awaited in this technical field.
Calcium pantothenate is a member of the vitamin-B group, water-soluble vitamins. Pantothenic acid is a component of coenzyme A and participates in acyl group transfer in vivo, playing important roles in the metabolism of lipids and carbohydrates. The lack of this vitamin causes disorders of the skin, adrenal gland, peripheral nerves, digestive tracts, antibody production, reproductive function, etc. Calcium ascorbate is a member of the vitamin-C group, water-soluble vitamins. Calcium ascorbate is absorbed in the digestive tracts and widely distributed over tissues in the body in the form of ascorbic acid, which has an antiscorbutic activity, promotes platelet production, and suppresses melanogenesis. The lack of ascorbate results in the vitamin C deficiency (scurvy, etc.).
Calcium pantothenate and calcium ascorbate are currently widely used for fodders, health foods, and pharmaceuticals, etc. However, there are no reports on the applicability of these compounds as a gelling agent.
An objective of the present invention is to provide a more effective gelling agent and a method for preparing gel using the gelling agent. The present inventors investigated the applicability of calcium pantothenate, a member of the vitamin-B group, or calcium ascorbate, a member of the vitamin-C group, to a gelling agent, specifically, for preparing alginate gel beads. Eventually, it was found that the gel was formed-by using the calcium salts of these acids at a suitable concentration, and thus the present invention was completed.
Namely, this invention relates to a method for preparing a gel composition utilizing a calcium salt of an acid as a gelling agent, more specifically, to:
(1) a method for preparing a gel composition, the method comprising using a calcium salt of an organic acid as a gelling agent;
(2) the method as described in (1), wherein the organic acid calcium salt is calcium pantothenate or calcium ascorbate;
(3) the method as described in (1), wherein the gel composition is alginate gel composition;
(4) the method as described in (1), wherein the gel composition contains chitosan or a salt thereof;
(5) a gel composition comprising calcium pantothenate or calcium ascorbate, which is obtainable in a single-step process of gel formation by mixing an aqueous solution of a substance having gelling capability and an aqueous solution of calcium pantothenate or calcium ascorbate;
(6) the gel composition as described in (5), wherein the organic salt is selected from the group consisting of lactic acid, ascorbic acid, gluconic acid, and citric acid;
(7) the gel composition as described in (5), wherein the substance having gelling capability is sodium alginate.
A calcium salt of an organic acid for preparing gel compositions used in the present invention is not particularly limited, but preferably calcium pantothenate or calcium ascorbate.
Calcium pantothenate may be isolated from natural sources such as yeasts, the liver, and others, or may be chemically synthesized by, for example, the condensation reaction of a calcium salt of xcex2-alanine and pantolactone to yield calcium d(+)-pantothenate (M. Catzi-Fichter: Helv. Chem. Acta., 24, 185 (1941)). In addition, pantothenic acid is known to be biosynthesized by enteric bacteria in mammals, and by yeasts, Escherichia coli and Neurospora crassa through the condensation of D-pantoic acid and xcex2-alanine in the presence of ATP (W. K. Mass, Proc. 4th Int. Congr. Biochem., Vol.11, p.161, Pergamon Press, London (1960)). Pantothenic acid used in the present invention can be synthesized by any of enzymes involved in such biosynthetic reactions. It can also be produced with a bioreactor using microorganisms such as yeasts, Escherichia coli, and Neurospora crassa mentioned above. There exist the D-enantiomer and L-enantiomer of pantothenic acid. Both calcium D-pantothenate and calcium L-pantothenate can be used as calcium pantothenate used in the present invention. Since the L-enantiomer does not possess the activity as the vitamin, the D-enantiomer should be used when the vitamin activity is required besides the function as a gelling agent.
Calcium ascorbate may be naturally occurring or chemically synthesized ones. The commercial product (Takeda Chemical Industries, Ltd.) can also be used. Ascorbic acid can be the D-enantiomer and L-enantiomer. Both calcium D-ascorbate and calcium L-ascorbate can be used as calcium ascorbate used in the present invention. The D-enantiomer does not possess the activity as the vitamin, and therefore the L-enaniomer should be used when the vitamin activity is required besides the function as a gelling agent.
A substance having gelling capability used in the method of this invention includes, for example, sodium alginate, pectin, carrageenan, agar, and gelatin. Any other substances that are gelled by calcium can be used in the method of this invention.
Chitosan used for preparing gel compositions in this invention includes chitosan having the glucosamine residue content (the degree of deacetylation) in its sugar chain of about 60% or more and average molecular weight of about 1500 to about 400,000.
When sodium alginate is used as the substance having gelling capability, a gel preparation can be produced using calcium pantothenate or calcium ascorbate by adding a 0.1 to 10% sodium alginate aqueous solution or an aqueous sodium alginate solution containing 1 to 10% chitosan dropwise to a aqueous solution of calcium pantothenate or calcium ascorbate, or a solution containing one of these calcium salts and 1 to 10% organic acid (for example, lactic acid, ascorbic acid, and gluconic acid, etc.) to form instantaneously alginate gel beads or chitosan salt-containing alginate gel beads. The concentration of calcium pantothenate used in this preparation ranges usually from about 0.03M to about 0.4M. The pH of the reaction system ranges usually from about 4.5 to about 7.0, and preferably about 6.0 to about 7.0. Calcium ascorbate is used in a concentration of about 0.02M to about 0.2M, and preferably about 0.1 to about 0.2M. The pH of the reaction system ranges usually from about 4.0 to about 7.0, and preferably about 4.5 to about 6.5. When a substance other than alginate gel is used as the substance having gelling capability, the pH in the reaction system should be adjusted so as not to inhibit the gel formation, preferably ranges from acidic to neutral pH.
Substances other than described above can be incorporated in the composition prepared by the method of this invention upon gellation. The substance to be incorporated is dissolved or suspended in a solution of alginic acid in advance, then can be easily trapped in the gel beads. The substance to be incorporated is not particularly liminted as long as it is solid or liquid. The method of this invention is advantageously applicable to substances that are decomposed by thermolysis and therefore are hardly incorporated in the gel such as agar by the conventional method. For example, multivitamin preparations can be prepared by incorporating other vitamins in the gel. When water-soluble vitamins is to be incorporated, the method of this invention is extremely advantageous in that the washing procedure to remove the gelling agent is not required. Incorporation of a chitosan salt capable of trapping taurocholic acid confers lipid metabolism-improving function on the gel preparation.
When cholestyramine, which causes constipation as the side effect, is incorporated, use of calcium pantothenate as a gelling agent can compensate the side effect of cholestyramine due to its ability to relieve constipation. Thus, the method of this inveniton is suitably applied to the manufacture of multivitamin preparations for improving lipid metabolism and vitamin-containing functional foods, which ameliorates atonic constipation. Moreover, ascorbic acid is known to reduce the cholesterol level, and accordingly, the method of this invention using calcium ascorbate as a gelling agent is suitably applied to the manufacture of pharmaceutical preparations or functional foods for treating hyperlipemia.